This invention relates to the manufacture of crimped polyamide filaments having excellent properties for use as rugs and carpets. More particularly, the invention relates to an improved method which imparts a stable crimp to polyamide filaments and which affords much higher operating speeds in processing the yarn.
Steam jet crimping processes are disclosed in Scott U.S. Pat. No. 3,143,784, Breen et al., U.S. Pat. Nos. 3,186,155, 3,421,194 and 3,543,358, Weiss U.S. Pat. No. 3,255,508 and Richmond et al., U.S. Pat. No. 3,380,242.
The Breen et al., U.S. Pat. No. 3,543,358 teaches that preferred speeds for feeding yarn to a steam jet are in the range of 100 to 800 yards per minute (90 to 720 meters per minute).
This invention provides a steam jet crimping process having feed yarn speeds which are higher than 800 meters per minute.
Such a high operating speed is accomplished in this invention by adopting particular conditions prior to steam jet crimping in a continuous process. Such particular conditions include melt spinning a non-circular cross section polyamide filament yarn, treating the yarn with a substantially non-aqueous oiling agent, applying one-sided heating and drawing steps substantially simultaneously, to the oil finished yarn while the yarn is passing over a heated body having a curved surface and, after that, applying heat treatment to the one-sided heated and drawn yarn. The heat treated yarn is then fed to a steam jet with speeds that are higher than 800 meters per minute, and are there subjected to steam jet crimping.